The present invention relates to a device for allowing elevator brake torque to be monitored and controlled.
The main shafts of escalators and the like, such as moving walkways, are provided with brake systems which, when set, prevent shaft rotation, and thus stop escalator movement. The brake system is set when power to the escalator is shut off. This can be during an emergency condition or when the escalator is otherwise powered down, such as for service. For the brake to function properly, it is imperative that the brake torque or force applied be sufficient to hold the shaft fast and prevent rotation. One way that this can be determined is by setting the brake and then applying a known torque to the set shaft through an electric motor, which is driven by a pwm-controlled source. Such a system is disclosed in published Japanese Application 01244065, published May 7, 1991. Such a system requires a relatively complicated control system for converting the desired torque to the equivalent motor drive input.
Alternatively, the condition of the brake can be checked during an escalator shut-down and maintenance procedure, wherein an appropriate scale is mounted to the brake arm, the brake manually set, and an increasing force or torque applied to the braked component. The application of such a force other than by energizing the shaft drive is often difficult to accomplish. In addition, if the escalator is activated for purposes of applying the force, there is a risk of injury to the maintenance personnel.
It is accordingly a purpose of the present invention to provide an apparatus for monitoring and measuring brake torque, particularly for purposes of insuring that the brake is functioning properly by being capable of withstanding certain minimal torque levels.
A further purpose of the present invention is to provide such a monitoring and measuring apparatus that can continuously monitor applied brake torque whenever the brake is activated.
Yet a further purpose of the present invention is to provide such a monitoring and measuring apparatus with the capability of generating output for a range of operating torques, to permit the determination of potential brake failure before it occurs.
In accordance with the foregoing and other objects and purposes, an automated brake torque monitoring system constructed in accordance with the present invention comprises a escalator brake having a brake torque arm. A torque sensor in mounted to the brake torque arm in a position such that it is exposed to brake torque during braking operation. The output of the sensor is thus a measure of the braking torque applied. Monitoring means process the output signal, which can be compared to reference values to determine whether the brake is performing in accordance with required specifications.